A navigation system uses an inertial measurement unit (IMU) to create a navigation solution. The IMU measures accelerations and turn rates, and a computing element integrates them over time to determine the position and attitude of an object. However, as an object travels for an extended period of time, errors in the measurements may arise and accumulate, causing the calculated position of the object to “drift” away from the object's true position. To correct these errors, external systems, like a global positioning system (GPS), can be used to provide correcting information. Nevertheless, signals from GPS or other external systems are unavailable in certain locations. Feature based navigation performed locally on a navigation system is one such method for acquiring information to correct drifting where correction information from external systems is unavailable.
Feature-based navigation systems acquire navigation information by detecting the positions of features within the environment of the object, and by relating changes in those positions to changes in position and attitude. For example, high resolution sensors can accurately detect the position of features within an environment by identifying specific, distinct features. A feature-based navigation system navigates by comparing the relative location of the identified features between frames. Some environments, such as non-structured natural environments, may not contain distinct features. In an environment with non-distinct features, feature-based navigation systems are unable to identify features. Further, other environments contain obscurants that block high frequency energy. The blocking of the high frequency energy causes high frequency, high resolution sensing systems to fail. While a sensor that emits low frequency energy can penetrate obscurants to resolve an image, the resultant images have low resolution and normal feature-based navigation methods are ineffective.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for improved systems and methods for navigation.